The bond between brass and rubber is believed to involve the formation of a thin layer of cuprous sulfide. During compounding and fabrication of the tire, the rubber picks up a small amount of water. Moreover, the presence of a layer of zinc hydroxide and/or oxide on the surface of the brass before use or the formation of zinc hydroxide and/or oxide by water in the rubber reacting with metallic zinc, leads to the very rapid growth of the cuprous sulfide layer and/or the formation of more zinc oxide and/or hydroxide. Some cuprous oxide, also, may be in these outer layers of the brass coating. These reactions are accelerated by the heat developed during operation of the tire. Thus, there is formed a relatively thick friable or weak layer of corrosion products where debonding can occur in said layer or between said layer and the brass and/or rubber strata.
Accordingly, it is an object of the present invention to overcome the difficulties alluded to above and to provide a method of treating brass to improve its adhesion to rubber.
Yet another object is to increase the resistance of the rubber-brass bond to degradation caused by heat and the presence of moisture.
A further object is to provide a brass-rubber composite exhibiting an improved brass-rubber bond.
Yet another object of this invention is to provide brass with a surface which is more amenable to bonding to rubber.
These and other objects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description and working examples.